Overview
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When following powertrain diagnostics on on-board diagnostic (OBD) vehicles, the system may be checked by an off board tester referred to as a scan tool. This article contains information for carrying out diagnostics with a scan tool. A scan tool has certain generic capabilities that are standard across the automotive industry in the United States. All functions are selected from a menu. Refer to the instruction manual provided by the scan tool manufacturer.
International Standards Organization (ISO) 14229 DTC Descriptions
The ISO 14229 DTC is a set of common requirements for diagnostic systems. The scan tool displays a failure type and a status type with the DTC. The types display additional information on the scan tool for the condition that set the DTC. For a list of failure type descriptions, refer to POWERTRAIN CONTROL SOFTWARE , International Standards Organization (ISO) 14229 Diagnostic Trouble Code (DTC) Descriptions.
Description
All on board diagnostic (OBD) scan tools support the clearing of continuous DTCs and resetting of emission monitors information in the PCM.
The clearing of the continuous DTCs allows the scan tool to command the PCM to clear and reset all emission-related diagnostic information. For more information about a drive cycle, refer to ON BOARD DIAGNOSTIC (OBD) DRIVE CYCLE .
The following events occur when the continuous DTCs and emission monitors information is cleared from the PCM
- the number of DTCs is reset
- the DTCs are cleared (on vehicles with permanent DTCs, additional vehicle operation is required to complete and pass the appropriate monitors to complete the clearing of permanent DTCs)
- the freeze frame data is cleared
- the diagnostic monitoring test results are reset
- the status of the OBD system monitors is reset
Resetting the KAM returns the powertrain control module (PCM) memory to its default setting. Adaptive learning contents such as idle speed, refueling event, and fuel trim are included. To clear the continuous diagnostic trouble codes (DTCs) in the PCM and have it reset the emissions monitors information, is also part of a KAM reset. Refer to CLEAR THE CONTINUOUS DIAGNOSTIC TROUBLE CODES (DTCS) AND RESET THE EMISSION MONITORS INFORMATION IN THE POWERTRAIN CONTROL MODULE (PCM) . Both can be useful in post repair retest.
After the KAM has been reset, the vehicle may exhibit certain driveability concerns. It is necessary to allow the engine to idle at normal operating temperature with the air conditioning (A/C) OFF for 2 minutes. To maintain the necessary idle time, enter the engine running diagnostic mode. Refer to DIAGNOSTIC MODES , Engine Running Diagnostic Mode in this article. Then drive the vehicle to allow the PCM to learn the values for optimum driveability and performance.
This function may not be supported by all scan tools. Refer to the scan tool manufacturer's instruction manual.
All on board diagnostic (OBD) scan tools display the OSR test. The OSR displays the supported monitors on the vehicle and the status of all monitors (complete or not complete) at that time. Fuel, misfire, and comprehensive component monitors (CCM) run continuously and always display YES status. Only clearing the diagnostic trouble codes (DTCs) from the powertrain control module (PCM) or resetting the keep alive memory (KAM) causes the non-continuous monitors to change to a NO status.
A detailed description of completing the OBD monitors is found in this article. Refer to ON BOARD DIAGNOSTIC (OBD) DRIVE CYCLE .
| WARNING | SAFETY MUST BE OBSERVED WHEN USING OSC. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY OR DEATH. |
The OSC aids in diagnosing output actuators associated with the PCM for the engine and the TCM for the transmission. This mode allows the technician to command the individual actuator state. For example: the output can be enabled or disabled, the duty cycle or the angle of the output can be increased or decreased. The OSC is used to help test the electrical, hydraulic or mechanical components of the vehicle. This function is supported by the vehicle strategy but may not be present on all vehicles or available on all scan tools.
Retrieve the continuous codes and carry out a key ON, engine OFF (KOEO) and key ON, engine running (KOER) on demand self-test before using any OSC. Any diagnostic trouble codes (DTCs) related to the transmission range (TR) sensor or the vehicle speed sensor (VSS) must be fixed or the PCM does not allow the OSC to operate.
The OSC has two options for operation, the Bench Mode and the Drive Mode. The Bench Mode is functional only when the vehicle gear selector is in the PARK or NEUTRAL position. The Bench Mode may be used when the engine is ON (running) or OFF (not running).
Each OSC function has a unique set of vehicle operating requirements that the technician is required to meet before operating the OSC. If the vehicle requirements are not met while commanding the OSC value, an error message appears. When the error message is received, OSC is canceled.
To confirm the scan tool sent the OSC value and the PCM has accepted the OSC substitution, a corresponding parameter identification (PID) for each OSC parameter must be monitored.
The parameter identification (PID) mode allows access to powertrain control module (PCM) information. This includes analog and digital signal inputs and outputs along with calculated values and the system status. There are two types of PID lists available and both are used throughout this article. The first is the generic (J1979) on board diagnostic (OBD) PID list. This is a standard set of PIDs that all scan tools must be able to access. The second is a Ford specific (J2190) PID list which can be accessed by an appropriate scan tool. When accessing any of these PIDs, they are continuously updated. The Generic or Ford PID list provides definitions and values in appropriate units.
Flash electrically erasable programmable read only memory (EEPROM) is contained in an integrated circuit internal to the PCM and TCM. The EEPROM contains the vehicle strategy including calibration information specific to the vehicle and is capable of being reprogrammed.
As part of the calibration there is an area referred to as the vehicle identification (VID) block in the PCM and the transmission identification (TRID) block in the TCM. Program the VID block when installing a new PCM as described under Programming the VID Block for a Replacement PCM, and program the TRID block as described under Programming the TRID Block for a Replacement TCM. Failure to carry out these procedures may generate diagnostic trouble codes (DTCs). The VID and TRID blocks in an existing PCM or TCM can also be tailored to accommodate various hardware changes made to the vehicle since production. Failure to carry out these procedures correctly may generate DTCs. The VID and TRID blocks contain many items used by the strategy for a variety of functions. Some of these items include the vehicle identification number (VIN), octane adjust, fuel octane, fuel type, vehicle speed limit, tire size, axle ratio, generator and traction motor resolver offsets, and the presence of speed control. Only items applicable to vehicle hardware and supported by the VID and TRID blocks are displayed on the scan tool.
When changing items in the VID or TRID blocks, the strategy places range limits on certain items such as tire and axle ratio. The VID and TRID blocks are also limited to the number of times they can be reconfigured. When this limit is reached, the scan tool displays a message indicating the need to flash the PCM or TCM again to reset the VID or TRID blocks.
Reprogramming can be carried out by a local Ford dealer or any non-Ford facility. Refer to the manufacturer's user manual for details.
Note. Clearing the continuous DTCs in the TCM can be carried out with the ignition in the ON position. It can also be carried out once the ignition is cycled to the START position, as long as the vehicle is in PARK.
Clearing the continuous DTCs in the TCM allows the scan tool to command the TCM to clear all DTCs along with freeze frame information.
The following events occur when the continuous DTCs are cleared in the TCM
- the number of DTCs are cleared
- the DTCs are cleared
- the freeze frame data is cleared
Note. After the TCM is successfully reprogrammed, clear the continuous diagnostic trouble codes (DTCs) in the powertrain control module (PCM) and the TCM that may have been stored during reprogramming.
Changes made to the strategy or calibration may require TCM reprogramming. Refer to the Module Programming instructions on the scan tool.
Description Of On Board Diagnostic (OBD) Drive Cycle
The following procedure is designed to execute and complete the OBD monitors. To complete a specific monitor for repair verification, follow steps 1 through 4, then continue with the step described by the appropriate monitor found under the OBD Monitor Exercised column. For the EVAP monitor to run, the ambient air temperature must be between 4.4 to 37.8°C (40 to 100°F), and the altitude below 2, 438 meters (8, 000 feet). If the OBD monitors must be completed in these conditions, the powertrain control module (PCM) must detect them once (twice on some applications) before the EVAP monitor can be bypassed and OBD monitors readied. The EVAP bypassing procedure is described in the following drive cycle.
Use a scan tool to carry out the OBD drive cycle. Refer to the scan tool manufacturers instruction manual for each described function.
A detailed description for clearing the DTCs is found in this article. Refer to CLEAR THE CONTINUOUS DIAGNOSTIC TROUBLE CODES (DTCS) AND RESET THE EMISSION MONITORS INFORMATION IN THE POWERTRAIN CONTROL MODULE (PCM) .